Grobstruktursimulation der atmosphärische Grenzschicht Übe partiell mit Meereis bedeckten Wasserf lachen
8 Heinemann, G., 1997: Idealized simu-
lations of the Antarctic katabatic wind system with a three-dimensional 'ra meso-scale rnodel. J. of Geophys.
2
Res., 102, 13825-1 3834. C,- 4
U- 3
Heinemann, G,, 1998: Katabatic wind and boundary layer front experiment around Greenland (KABEG) field 1 phase report. Reports on Polar ße
search, 269, Alfred-Wegener-Institute t i m e (h) for Polar Research, Bremerhaven,
FRG, 93pp. Fig.3: Time series of the near-surface wind speed (ff), temperature (T2m) and net radiation (Q) for point K shown in Fig.l for the idealized simulation for March.
Acknowledgments
The numerical simulations were funded by DFG under grant He274011.
Corresponding author address: G. Heinemann, Meteorologisches Institut der Universitä Bonn, Auf dem Hüge 20, D53121 Bonn, Germany. (email: gheinemannauni-bonn.de)
5 4
ÖGRILAS Früh Öffnungsgeschicht der Lazarev-See und der Riiser-Larsen- See
-
Kompilation und Interpretation neuer geophysikalischer Datensätz K. ~ i n z l , Y.B. ~ o u s e v a ~ , G.A. ~ u d r ~ a v t s e v ~ , S.
eben',
H.A. ~ o e s e r '1 - Bundesanstalt fü Geowissenschaften und Rohstoffe (BGR), Hannover
2 - Polar Marine Geological Research Expedition (PMGRE), St. Petersburg
Fü die plattentektonische Rekonstruktion der Öffnungsgeschicht des südwestliche Indischen Ozeans und die Separation Gondwanas in Antarktis, Afrika, Madagaskar und Indien liegen zahlreiche Modelle vor, die Widersprüch und Diskrepanzen auf- weisen. Der Hauptgrund fü die Unterschiede ist die noch immer relativ geringe Dichte an geophysikalischen Profilen in den Seegebieten der Ostantarktis. Im Süd Sommer 1995196 wurde von der BGR mit der AKADEMIK NEMCHINOV ein verdich- tendes Netz geophysikalischer Profile in der Lazarev-See, auf dem Astrid-Rücke und in der Riiser-Larsen-See vermessen. Zusammen mit einem Profilnetz, das von der PMGRE (St. Petersburg) mit der AKADEMIK A. KARPINSKI in der Riiser-Larsen- See vermessen wurde, stehen jetzt insgesamt übe 7.200 km neue seegeophysikali- sehe Daten (mehrkanalige Reflexionsseismik, Refraktionsseismik, Gravimetrie und Magnetik) zur Verfügung Weiterhin sind auf sechs Flugprofilen des AWI magneti- sche Daten gewonnen worden.
Die umfangreichen und qualitativ hochwertigen neuen Datensätz erlauben in Kombi- nation mit den schon vorliegenden Vermessungen die Erstellung einer verbesserten Strukturkarte, die einige wichtige Befunde zeigt.
Die vulkanische Einheit des zuerst in der Weddell-See erkannten EXPLORA- Wedges, bei dem es sich um ein mächtige Schichtpaket mit seewärt einfallenden Reflektoren und hoher Magnetisierung handelt, zieht sich nach Osten bis 12OE an den Fuà des Astrid-Rückens Die maximale seewärtig Ausdehnung dieser Struktur beträg dabei 120 km.
Der Astrid-Rücke wird durch die Astrid-Transformstörun bei 67'20's in einen nörd lichen und einen südliche Teil getrennt. Im südliche Teil haben sich nach dem re- flexionsseismischen Bild vulkanische Komplexe auf vermutlich kontinentaler Kruste gebildet. Das Magnetfeld ist in einigen Bereichen des südliche Astrid-Rücken viel ruhiger als im nördliche Teil des Rückens in dem auch reflexionsseismisch groß Machtigkeiten basischer Vulkanite beobachtet worden sind.
Die zentrale Riiser-Larsen-See ist von ozeanischer Kruste mit auffallend flachem Re- lief unterlagert. In Analogie zu unseren Befunden im Südatlanti schließe wir daraus auf eine erhöht magmatische Aktivitä währen der Entstehung dieses Gebietes. Die Identifizierung der magnetischen Lineationen M22 bis M1 in der Riiser-Larsen-See konnte mit den neuen Daten weiter verfeinert werden. Einige Bruchzonen sind in Ost- West-Profilen mit Stufen in der Basementtiefe korreliert, deren Prägnan von Süde nach Norden zuzunehmen scheint.
Die aeromagnetischen Profile in der Riiser-Larsen-See zeigen im Bereich des Konti- nentalhangs weiträumig positive Anomalien, die den Übergan von kontinentaler zu ozeanischer Kruste markieren könnten Diese Linie liegt 75 - 125 km landwärt von Anomalie M24 (153 Mill. Jahre). Wenn wir die später Spreadingrate 1,7 cm/Jahr bis zur 0.g. weiträumige Anomalie extrapolieren, ergibt sich bei Verwendung der Zeits- kala GTS89 von Harland et al. fü den Beginn der Driftphase ein Alter von 159 Mill.
Jahren,
Studies On antarctic bacterial isolates from soils and from hypersaline a n d heliothermal Ekho Lake (Vestfold Hills, East Antarctica)
Peter Hirsch & Matthias Labrenz
Institut fü Allgemeine Mikrobiologie, Am Botanischen Garten 1-9, 241 18 Kiel The investigations were carried out with 52 bacterial isolates that came from the hypersaline, heliothermal and merornictic Ekho Lake, and 67 cultures from seven soils which had anthropogenic contamination of different degrees. Our interests were as follows: (l)To describe the Ekho Lake isolates (most of which appeared to be new) On the species or even genus level after sequence analysis of their 1 6 s rDNA.
Also, to study possible physiological adaptations of the isolates to their natural habitat, and to apply to these a new method for species- and 1 or strain differentiation. (11) Likewise, to deterrnine the proportions of unknown genera and species among the isolates obtained from soils with different degrees of anthropogenic contarnination. (111) Exoenzyrnatic activities of the soil islates were to be compared to those observed during in situ experiments. Thus, a major question was, if comparibly more known species would be present in the possibly contaminated antarctic soils, than in the presumably pristine Ekho Lake.
I Description of new genera and species isolated from the Ekho Lake
Manuscripts with the descriptions of two new genera have been subrnitted and reviewed.
l.1.a. Antarctobacter heliothermus gen. nov., sp. nov. (2, 4). These were Gram- negative, aerobic, pointed and budding bacteria with storage granules and rosette formation. Daughter cells could be motile. Growth required sodium ions; nitrate was reduced to nitrite, DNase and gelatinase were produced. Glutamate was metabolized with and without an additional source of combined nitrogen. The most abundant fatty acid was C18:q, other fatty acids present in lower concentrations were C12:1 3-OH, c16:1, c16:0, c18:0, and C1g:o Main polar lipids were phosphatidylglycerol and phosphatidylcholine. The DNA base composition was 62.3 to 62.8 mol% G+C. 16s rDNA sequence comparisons showed the isolates to be phylogenetically related to the genera Sagittula and Roseobacter. The type strain is EL-21gT (= DSM 11445).
1.1.b. Roseovarius tolerans gen. nov., sp. nov. (3, 4). These Gram-negative, aerobic, pointed and budding bacteria also contained storage granules and had motile daughter cells. Bacteriochlorophyll a could be produced, but it was repressed by constant dim light. The strains tolerated a wide range of temperatures, of pH, and concentrations of artificial seawater (ASW) or NaCI, but they had an absolute requirement for ~ a ' . Glutamate was metabolized with and without additional combined nitrogen. The dominant fatty acid was C q à § : ~ other characteristic fatty acids were C18:2, C 1 2 9 2-OH,
Cl211
3-QH, Cjg:q, C16:o and Cl8:0. Main polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine. The DNA base composition was 62 to 64 mol% G+C. 16s rRNA gene sequence comparisons showed the isolates to be close phylogenetic neighbours of Antarctobacter', 'Marinosulfonomonas', Octadecabacter, Sagittula, Sulfitobacter and Roseobacter. Type strain: EL-1 721' (= DSM 1 1457).1.2 Physiological adaptations to the natural habitat in Ekho Lake. Osmotolerance was tested with ASW. In most cases, the organisms tolerated higher concentrations of ASW than of NaCI. ASW was also more similar to the "salinities" measured at their natural habitat, i.e. in the Lake.
1.3 A new method for the differentiation of species and 1 or strains: The analysis of 16s-23s rDNA internal transcribed spacer (ITS). In order to examine the intra- and interspecific biodiversity of Roseobacter denitrificans, R. litoralis, R. algicola, 'Antarctobacter heliothermus' and 'Roseovarius tolerans', their highly variable 16S- 23s rDNA ITS were amplified and analyzed for fragment lengths and DNA sequences. 'A. heliothermus' had strains with an ITS-fragment length of 1092 bp. R.
tolerans consisted of 8 strains; 5 of them had two ITS-fragments of different lengths (959 and nearly 1100 bp), whereas 3 harbored only one fragment of 1083 bp (2 strains) or 1165 bp (one strain). Despite the obvious length variations within the ITS- fragments, phylogenetic relationsships could not be found with ITS length data. In contrast, the alignment of ITS-DNA sequences and neighbor-joining/parsimony trees revealed a highly corresponding and well supported phylogenetic tree. The strains of both new genera formed a monophyletic branch where they were well separated from each other and from type strains of Roseobacter species (4).
II. Proportions of known genera and species among the antarctic soil isolates H.a. Identification of bacteria by sequence analysis of the 16s rDNA. So far, nine bacterial strains were investigated by 16s rRNA sequencing; six other strains are presently being studied. The nine strains belonged to five already known species, all of them were members of previously described genera. Surprisingly, Eminia amylovora had come from the presumably pristine Ice Plateau.
III. Exoenzymatic activities. Strains were tested which came from sites where in situ exposure of fluorogenic substrate analoges to the antarctic soil profile had been carried out. Sterile filter paper strips had been soaked in 4-methylumbelliferyl- containing substrate analoges and were pressed for various periods of time against the soil profile (1). These strains showed, when tested in the laboratory for hydrolysis of these substrate analoges, that they were definitely capable of enzymatic release and possibly utilization of the substrates.
References
1. Hirsch, P., Labrenz, M. & Peissl, K. (1998). In situ demonstration of microbial exoenzymatic activity in three antarctic soil profiles using fluorogenic substrate analogues. Manuscript in preparation.
2. Labrenz, M., Collins, M. D., Lawson, P., Tindall, B. J., Braker, G. & Hirsch, P.
(1998a). Antarctobacter heliothermus gen. nov., sp. nov., a budding bacterium from hypersaline and heliothermal Ekho Lake. Int J Syst Bacteriol. Submitted.
3. Labrenz, M., Collins, M. D., Lawson, P., Tindall, B. J., Schumann, P. & Hirsch, P. (1998b). Roseovarius tolerans gen. nov., sp. nov., an aerobic, budding and variable bacteriochlorophyll a producing bacterium from hypersaline, heliothermal and meromictic Ekho Lake (Vestfold Hills, East Antarctica). Int J Syst Bacteriol.
Submitted.
4. Söller R., Labrenz, M. & Hirsch, P. (1998). Molecular diversity of the 16s-23s rDNA internal transcribed spacer (ITS) of Roseobacter, Roseovarius, and Antarctica. In BIOspektrum, Abstracts, VAAM-Tagung Frankfurt, (PF114).
Heidelberg: Spektrum Akademischer Verlag GmbH.